Handover between non-standalone and standalone networks

ABSTRACT

Systems, devices, and techniques described herein relate to handover between Non-Standalone (NSA) and Standalone (SA) networks. An example method includes receiving, from a User Equipment (UE), a measurement report indicating that a signal threshold has been satisfied. In response to receiving the measurement report, handover of a communication session from a first core network to a second core network may be initiated. A message confirming that the communication session has been handed over from the first core network to the second core network can be received. In response to receiving the message, handover of the communication session can be initiated between a single radio bearer associated with a first Radio Access Technology (RAT) and a dual radio bearer associated with the first RAT and a second RAT.

CROSS-REFERENCE TO RELATED APPLICATION

The present patent application claims priority to U.S. ProvisionalApplication No. 62/824,186, filed on Mar. 26, 2019, which isincorporated by reference herein in its entirety.

BACKGROUND

Cellular communication devices use network radio access technologies tocommunicate wirelessly with geographically distributed cellular basestations. Long-Term Evolution (LTE) is an example of a widelyimplemented radio access technology that is used in 4th Generation (4G)communication systems. New Radio (NR) is a newer radio access technologythat is used in 5th Generation (5G) communication systems. Standards forLTE and NR radio access technologies have been developed by the 3rdGeneration Partnership Project (3GPP) for use by wireless communicationcarriers.

A communication protocol defined by the 3GPP, referred to as EN-DC(Evolved Universal Terrestrial Radio Access Network (E-UTRAN)/NewRadio-Dual Connectivity) enables the simultaneous use of LTE and NRradio access technologies for communications between a mobile device anda cellular communication network. EN-DC may also be referred to asLTE/NR dual connectivity. EN-DC is described by 3GPP TechnicalSpecification (TS) 37.340.

EN-DC can be implemented in conjunction with a 4G core network, with thesupport of 5G base stations, in a configuration known as Non-StandaloneArchitecture (NSA). In this configuration, a 4G LTE base station(referred to as a Master eNodeB or MeNB) is associated (e.g., via an X2interface) with a 5G NR base station (referred to as a Secondary gNodeBor SgNB). In an NSA system, both the LTE base station and the NR basestation support a 4G core network. However, control communications arebetween the 4G core network and the LTE base station, and the LTE basestation is configured to communicate with and to control the NR basestation.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items or features.

FIG. 1 illustrates an example environment for handover betweenNon-Standalone (NSA) and Standalone (SA) network environments.

FIG. 2 illustrates an example environment illustrating interfaces andvarious elements of an NSA network architecture and an SA networkarchitecture.

FIG. 3 illustrates example signaling or performing handover of a sessionbetween an NSA network and an SA network.

FIG. 4 illustrates a process for handing over a session between anetwork having an NSA architecture and a network having an SAarchitecture.

FIG. 5 illustrates a process for transferring session context duringhandover between a network having an NSA architecture and a networkhaving an SA architecture.

FIG. 6 illustrates example devices configured to initiate handoverbetween an NSA network and an SA network

DETAILED DESCRIPTION

The systems, devices, and techniques described herein relate to handoverof communication sessions between Non-Standalone (NSA) and Standalone(SA) networks. In various implementations, handover of a communicationsession between a User Equipment (UE) and a particular networkarchitecture can be triggered based on radio conditions experienced bythe UE.

In some implementations, a communication session provided to a UE over adual radio bearer provided by a first base station in an NSA network canbe handed over to a single radio bearer provided by a second basestation in an SA network. For instance, upon receiving a report that apower or quality of a radio signal over the single radio bearer exceedsa particular threshold and/or that a power or quality of a radio signalover the dual radio bearer is below a certain threshold, the first basestation may cause a first core network associated with the NSA networkto hand over the communication session to a second core networkassociated with the SA network. In response to receiving a messageindicating that the communication session has been handed over to thesecond core network, the first base station may cause the communicationsession to be handed over from the dual radio bearer to the single radiobearer provided by the second base station. The first base station mayalso sever the dual radio bearer between the first base station and theUE.

In various examples, a communication session provided to a UE over asingle radio bearer provided by a third base station in an SA networkcan be handed over to a dual radio bearer provided by a fourth basestation in an NSA network. For instance, upon receiving a report that apower or quality of a radio signal received by the UE is below aparticular threshold, the third base station may cause a third corenetwork associated with the SA network to hand over the communicationsession to a fourth core network associated with the NSA network. Inresponse to receiving a message indicating that the communicationsession has been handed over to the fourth core network, the third basestation may cause the communication session to be handed over from thesingle radio bearer to the dual radio bearer provided by the fourth basestation. The third base station may also sever the single radio bearerbetween the third base station and the UE.

According to various examples, a single radio bearer may be a 5G (e.g.,NR) radio bearer. The dual radio bearer may include a 5G radio bearerand a 4G (e.g., LTE) radio bearer. In some cases, the single 5G radiobearer may utilize higher frequency radio spectrum than the 4G radiobearer in the dual radio bearer. Higher frequency radio signals mayexperience higher attenuation than lower frequency radio signals.Accordingly, a coverage area of the single 5G radio bearer may besmaller than a coverage area of the 4G radio bearer. Due to theinclusion of the 4G radio bearer, the dual radio bearer may beconfigured to provide services wirelessly to UEs located in a broaderarea than the single 5G radio bearer.

However, in some cases, the 4G radio bearer may be provided usinglimited resources. For instance, the 4G radio bearer may be associatedwith one or more channels in a limited amount of 4G radio resources(e.g., frequency spectrum). Thus, it may be advantageous to avoid theuse of the 4G radio bearer in order to conserve the 4G radio resources.

In some cases, a base station managing handover (e.g., the first basestation or the third base station) may also forward context data relatedto the communication session to the next base station (e.g., the secondbase station or the fourth base station). For example, the base stationmanaging handover may be receiving data in the communication sessionduring the handover process. When the managing base station hands overthe communication session to the next base station, the managing basestation may also transmit the data received during the handover processto the next base station.

Various implementations of this disclosure relate to managing physicalradio bearers based on measurements of radio conditions. Accordingly,example implementations can apply to practical applications inreal-world environments.

In addition, various implementations provide specific improvements tothe field of telecommunications. For instance, selective handover of aUE between SA and NSA radio bearers may enable a RAN to conserve LTEradio resources while still maintaining a high transfer rate and qualityof data received by the UE.

FIG. 1 illustrates an example environment 100 for handover betweenNon-Standalone (NSA) and Standalone (SA) network environments. As usedherein, the terms “Non-Standalone,” “Nonstandalone,” “NSA,” and theirequivalents can refer to a telecommunications network architecture thatcan utilize multiple Radio Access Technologies (RATs) to deliverservices to end UEs. In some cases of NSA architectures, 5th Generation(5G) services can be provided to users using existing 4th Generation(4G) architecture.

The NSA network environment may include a dual bearer Radio AccessNetwork (RAN) 102 associated with a dual bearer coverage area 104. Asused herein, the term “RAN” and its equivalents may refer to a networkincluding at least one of a 3GPP RAN, such a GSM/EDGE RAN (GERAN), aUniversal Terrestrial RAN (UTRAN), or an Evolved UTRAN (E-UTRAN), a 5GUTRAN, or alternatively, via a “non-3GPP” RAN, such as a Wi-Fi RAN, oranother type of wireless local area network (WLAN) that is based on theIEEE 802.11 standards. In some instances, a RAN can include a Wi-FiAccess Point (AP). In some cases, a RAN can include an eNodeB, a gNodeB,or a combination thereof. For instance, the dual bearer RAN 102 mayinclude an eNodeB (configured to wirelessly transmit and/or receivesignals over one or more Long Term Evolution (LTE) bands) and a gNodeB(configured to wirelessly transmit and/or receive signals over one ormore New Radio (NR) bands).

In various examples, the dual bearer RAN 102 may be connected to a 4Gcore network (e.g., an Evolved Packet Core (EPC)) (not illustrated) andis associated with Option 3, Option 3A, Option 3X, or the like. Inexamples referred to as “Option 3,” user plane data may be transmittedbetween an end UE and the 4G RAN, between the end UE and the 5G RAN,between the 4G RAN and the 5G RAN, and between the 4G RAN and the 4Gcore network. In Option 3, control plane data may be transmitted betweenthe end UE and the 4G RAN, between the 4G RAN and the 5G RAN, andbetween the 4G RAN and the 4G core network. In various implementationsof Option 3, both user plane data and control plane data may betransferred through the 4G RAN.

In examples referred to as “Option 3A,” user plane data may betransmitted between an end UE and the 4G RAN, between the end UE and the5G RAN, between the 4G RAN and the 4G core network, and between the 5GRAN and the 4G core network. In Option 3A, control plane data may betransmitted between the end UE and the 4G RAN, between the 4G RAN andthe 5G RAN, and between the 4G RAN and the 4G core network. In variousinstances of Option 3A, user plane data may be transferred through the4G RAN and/or the 5G RAN, and control plane data may be transferredthrough the 4G RAN.

In examples referred to as “Option 3X,” user plane data can betransmitted between the 5G RAN and the end UE via a 5G radio bearer,between the 5G RAN and the 4G RAN, and between the 5G RAN and the 4Gcore network. In addition, in Option 3X, control plane data may betransmitted between the 4G RAN and the UE, between the 4G RAN and the 5GRAN, and between the 4G RAN and the 4G core network. Accordingly, inOption 3X, user plane data may be transferred through the 5G RAN andcontrol plane data may be transferred through the 4G RAN. Examples inwhich the dual bearer RAN 102 is associated with Option 3X will bedescribed in further detail below with respect to FIG. 2.

NSA architectures, such as architectures including the dual bearer RAN102, can support dual connectivity. As used herein, the terms “dualconnection,” “dual bearer,” or the like can refer to a radio bearersimultaneously utilizing at least two types of RATs. For instance, adual bearer may include a 4G radio bearer and a 5G radio bearer.According to some examples, user plane data may be transmitted between a4G core network and an end UE simultaneously via a 4G RAN and a 5G RANin various NSA deployments.

The SA network environment illustrated in FIG. 1 may include a singlebearer RAN 106 associated with a single bearer coverage area 108. Asused herein, the terms “Standalone,” “SA,” and their equivalents canrefer to a telecommunications architecture in which a core network canutilize a single RAT to deliver services to end UEs. For instance, inexamples of an “Option 1” deployment, user plane data and control planedata between a 4G core network and an end UE may be transferred througha 4G RAN. In examples of an “Option 2” deployment, user plane data andcontrol plane data between a 5G core network (e.g., a 5G Core (5GC)) andan end UE may be transferred through a 5G RAN. In some examples of an“Option 5” deployment, user plane data and control plane data between a5G core network and an end UE may be transferred through a 4G RAN.

A User Equipment (UE) 110 may move throughout the dual bearer coveragearea 104 and/or the single bearer coverage area 108. As used herein, theterms “UE,” “user device,” “wireless communication device,” “wirelessdevice,” “communication device,” “mobile device,” “client device,” and“terminal” can be used interchangeably herein to describe any UE (e.g.,the first UE 110) that is capable of transmitting/receiving datawirelessly using any suitable wireless communications/data technology,protocol, or standard, such as Global System for Mobile Communications(GSM), Time Division Multiple Access (TDMA), Universal MobileTelecommunications System (UMTS), Evolution-Data Optimized (EVDO), LongTerm Evolution (LTE), Advanced LTE (LTE+), New Radio (NR), GenericAccess Network (GAN), Unlicensed Mobile Access (UMA), Code DivisionMultiple Access (CDMA), Orthogonal Frequency Division Multiple Access(OFDM), General Packet Radio Service (GPRS), Enhanced Data GSMEnvironment (EDGE), Advanced Mobile Phone System (AMPS), High SpeedPacket Access (HSPA), evolved HSPA (HSPA+), Voice over Internet Protocol(IP) (VoIP), VoLTE, Institute of Electrical and Electronics Engineers'(IEEE) 802.1x protocols, WiMAX, Wi-Fi, Data Over Cable Service InterfaceSpecification (DOCSIS), digital subscriber line (DSL), and/or any futureIP-based network technology or evolution of an existing IP-based networktechnology.

In general, the UE 110 can be implemented as any suitable type ofcomputing device configured to communicate over a wired or wirelessnetwork, including, without limitation, a mobile phone (e.g., a smartphone), a tablet computer, a laptop computer, a Portable DigitalAssistant (PDA), a wearable computer (e.g., electronic/smart glasses, asmart watch, fitness trackers, etc.), an Internet-of-Things (IoT)device, an in-vehicle (e.g., in-car) computer, and/or any similar mobiledevice, as well as situated computing devices including, withoutlimitation, a television (smart television), a Set-Top-Box (STB), adesktop computer, and the like.

When the UE 110 is located in the dual bearer coverage area 104, the UE110 may be configured to transmit and/or receive data over a dual 4G/5Gbearer 112 provided by the dual bearer RAN 102. The dual 4G/5G bearer112 may include at least two radio bearers: one 4G (e.g., LTE) radiobearer and one 5G (e.g., NR) radio bearer. As used herein, the terms“radio bearer,” “radio link,” “radio channel,” or their equivalents, canrefer to one or more radio resources over which data can be transmittedwirelessly between at least two nodes in a network. According to variouscases, a radio bearer may be defined according to one or more frequencybands, one or more time intervals, or a combination thereof. In someexamples, a radio bearer carrying user plane data may be referred to asa “Data Radio Bearer (DRB).” For instance, services (e.g., voiceservices) may be transmitted over one or more DRBs. A radio bearercarrying control plane data may be referred to as a “Signaling RadioBearer (SRB).” For instance, Radio Resource Control (RRC) messages andNon-Access Stratum (NAS) signals may be transmitted over one or moreSRBs.

As used herein, the term “5G radio bearer” and its equivalents can referto a radio bearer utilizing one or more 5G-specific radio resourcesand/or a 5G-specific signaling protocol. For instance, in variousimplementations, at least one of NR bands n71, n260, and/or n261 may bespecifically allocated to 5G radio signaling. In some cases, 5G-specificradio resources may include millimeter wave radio resources, such asresources within n260 and/or n261.

As used herein, the term “4G radio bearer” and its equivalents can referto a radio bearer utilizing one or more 4G radio resources and/or a 4Gsignaling protocol. In some cases, at least one of LTE bands 2, 12, 66,or 71 may be allocated to 4G radio signaling.

When the UE 110 is located in the single bearer coverage area 108, theUE 110 may be configured to transmit and/or receive data over a single5G bearer 114 provided by the single bearer RAN 106. In variousimplementations, the single 5G bearer 114 may be a 5G radio bearer.

In various implementations, the UE 110 may move between a Position A 116and a Position B 116 while being engaged in an ongoing communicationsession. In some cases, the communication session may be handed overbetween the NSA network environment (e.g., including the dual bearer RAN102) and the SA network environment (e.g., including the single bearerRAN 106).

In various instances, the UE 110 may be located at Position A and may beutilizing the NSA network architecture. The UE 110 may be transmittingand/or receiving data wirelessly with the dual bearer RAN 102 over thedual 4G/5G bearer 112. The data may be at least part of the existingcommunication session.

The dual bearer RAN 102 may transmit at least one message indicating oneor more radio thresholds. For instance, the dual bearer RAN 102 maytransmit an RRC configuration message that indicates a first thresholdthat can be compared to a signal received from the single bearer RAN106. In some cases, the RRC reconfiguration message may further indicatea second threshold that can be compared to a signal received from thedual bearer RAN 102. For example, the RRC reconfiguration message mayspecify at least one B2 event.

In example instances, the dual bearer RAN 102 may transmit, to the UE110, a first RRC reconfiguration message indicating the first thresholdand a second RRC reconfiguration message indicating the secondthreshold. In some examples, at least one of the first threshold or thesecond threshold may include a power threshold, such as a ReceivedSignal Strength Indicator (RSSI), a Reference Signal Received Power(RSRP), or the like. In some cases, at least one of the first thresholdor the second threshold may include a signal quality threshold, such asa Reference Signal Received Quality (RSRQ), a Signal to Interferenceplus Noise Ratio (SINR), or the like.

The RRC reconfiguration message(s) transmitted by the dual bearer RAN102 to the UE 110 may further identify the signal from the single bearerRAN 106 that can be compared to the first threshold and/or the signalfrom the dual bearer RAN 102 that can be compared to the secondthreshold. For instance, the RRC configuration message(s) may identifythe type of signal by at least one of a channel, a frequency, a band, aslot, a subframe, or the like, in which the signal to be measured willbe transmitted. In various implementations, the signal to be compared tothe first threshold is transmitted by the single bearer RAN 106 in a5G-specific band (e.g., a millimeter wave band, n71, n260 and/or n261).In some cases, the signal to be compared to the second threshold istransmitted by the dual bearer RAN 102 in a 4G-specific band (LTE bands2, 12, and/or 66) and/or a shared 4G/5G band (e.g., LTE band 71 and NRband n71).

The UE 110 may receive wireless signals from the single bearer RAN 106and compare the wireless signals to the first threshold. In variousexamples, the UE 110 may receive wireless signals from the dual bearerRAN 102 and compare the wireless signals to the second threshold. If theUE 110 determines that the signals from the single bearer RAN 106 areabove the first threshold and/or that the signals from the dual bearerRAN 102 are below the second threshold, the UE 110 may transmit a reportto the dual bearer RAN 102. For instance, the UE 110 may move fromPosition A 116 to Position B 118, thereby moving to a cell edge of thedual bearer coverage area 104 and entering the single bearer coveragearea 108.

Upon receiving the report from the UE 110, the dual bearer RAN 102 maycause the communication session to be handed over from the dual bearerRAN 102 to the single bearer RAN 106. In some cases, the dual bearer RAN102 may request a first core network associated with the dual bearer RAN102 (e.g., an EPC) to hand over the communication session to a secondcore network associated with the single bearer RAN 106 (e.g., a 5GC).The first core network may request the second core network to transferthe communication session. When the second core network has confirmed,to the first core network, that the communication session has beentransferred, the first core network may report, to the dual bearer RAN102, that the communication session has been handed over to the secondcore network.

In response to identifying that the communication session has beenhanded over to the second core network, the dual bearer RAN 102 mayinitiate handover of the communication session to the single bearer RAN106. In various examples, the dual bearer RAN 102 may transmit, to theUE 110, an instruction to connect to the single bearer RAN 106. Theinstruction may be, for instance, in an RRC reconfiguration message.

When the UE 110 receives the instruction from the dual bearer RAN 102,the UE 110 may establish a connection with the single bearer RAN 106.For instance, the UE 110 and the single bearer RAN 106 may exchangeSession Initiation Protocol (SIP) messages and/or may synchronize. TheUE 110 may attach to the single bearer RAN 106. Because thecommunication session has already been transferred to the second corenetwork associated with the single bearer RAN 106, the UE 110 may beenabled to immediately transmit and/or receive data in the communicationsession via the single 5G bearer 114 provided by the single bearer RAN106.

In various cases, the process of transferring the session from the firstcore network to the second core network may take a non-negligible amountof time. Further, the process of transferring the session from the dualbearer RAN 102 to the single bearer RAN 106 may also take anon-negligible amount of time. During these latency periods, the dualbearer RAN 102 may continue receiving data in the communication session.This data may be referred to as a “session context,” “context data,” ortheir equivalent terminology. To ensure that the session context isretained during handover from the NSA network architecture to the SAnetwork architecture, the dual bearer RAN 102 may further cause thesession context to be transmitted to the single bearer RAN 106. Forinstance, the dual bearer RAN 102 may transmit the session context tothe first core network, which may transfer the session context to thesecond core network, which may deliver the second context to the singlebearer RAN 106.

In some implementations, the dual bearer RAN 102 may also end the dual4G/5G bearer 112. For example, the dual bearer RAN 102 may sever thedual 4G/5G bearer 112 in response to transmitting the instruction to theUE 110 to transfer the session to the single bearer RAN 106.

In various implementations, the communication session may be handed overfrom the single bearer RAN 106 to the dual bearer RAN 102. For instance,the UE 110 may be transmitting and/or receiving data via a the single 5Gbearer 114. The data may be part of the communication session.

The single bearer RAN 106 may transmit a message indicating a radiothreshold. For instance, the single bearer RAN 106 may transmit an RRCreconfiguration message that indicates a third threshold that can becompared to a signal received from the dual bearer RAN 102. For example,the RRC reconfiguration message may specify an A4 event.

In example instances, the third threshold may include a power threshold,such as an RSSI, an RSRP, or the like. In some cases, the thirdthreshold may include a signal quality threshold, such as an RSRQ, aSINR, or the like. According to some implementations, the thirdthreshold may be the same as the first threshold.

The RRC reconfiguration message transmitted by the single bearer RAN 106to the UE 110 may further identify the signal from the dual bearer RAN106 that can be compared to the third threshold. For instance, the RRCreconfiguration message(s) may identify the type of signal by at leastone of a channel, a frequency, a band, a slot, a subframe, or the like,in which the signal to be measured will be transmitted. In some cases,the signal to be compared to the third threshold is transmitted by thedual bearer RAN 102 in a 4G-specific band (LTE bands 2, 12, and/or 66)and/or a shared 4G/5G band (e.g., LTE band 71/n71).

The UE 110 may receive wireless signals from the dual bearer RAN 102 andcompare the wireless signals to the third threshold. If the UE 110determines that the signals from the dual bearer RAN 102 are above thethird threshold, the UE 110 may transmit a report to the single bearerRAN 106. For instance, the UE 110 may move from Position B 118 toPosition A 116, thereby leaving the single bearer coverage area 108 andentering a mid-cell region of the dual bearer coverage area 104.

Upon receiving the report from the UE 110, the single bearer RAN 106 maycause the communication session to be handed over from the single bearerRAN 106 to the dual bearer RAN 102. In some cases, the single bearer RAN106 may request the second core network associated with the singlebearer RAN 106 (e.g., a 5GC) to hand over the communication session tothe first core network associated with the dual bearer RAN 102 (e.g., anEPC). The second core network may request the first core network totransfer the communication session. When the first core network hasconfirmed, to the second core network, that the communication sessionhas been transferred, the second core network may report, to the singlebearer RAN 106, that the communication session has been handed over tothe first core network.

In response to identifying that the communication session has beenhanded over to the first core network, the single bearer RAN 106 mayinitiate handover of the communication session to the dual bearer RAN102. In various examples, the single bearer RAN 106 may transmit, to theUE 110, an instruction to connect to the dual bearer RAN 102. Theinstruction may be, for instance, in an RRC reconfiguration message.

When the UE 110 receives the instruction from the single bearer RAN 106,the UE 110 may establish a connection with the dual bearer RAN 102. Forinstance, the UE 110 and the single bearer RAN 106 may exchange SIPmessages and/or may synchronize. The UE 110 may attach to the dualbearer RAN 102. Because the communication session has already beentransferred to the first core network associated with the dual bearerRAN 102, the UE 110 may be enabled to immediately transmit and/orreceive data in the communication session via the dual 4G/5G bearer 112provided by the dual bearer RAN 102.

In various cases, the process of transferring the session from thesecond core network to the first core network may take a non-negligibleamount of time. Further, the process of transferring the session fromthe single bearer RAN 106 to the dual bearer RAN 102 may also take anon-negligible amount of time. During these latency periods, the singlebearer RAN 106 may continue receiving session context data. To ensurethat the session context is not lost during handover from the SA networkto the NSA network, the single bearer RAN 106 may further cause thesession context to be transmitted to the dual bearer RAN 102. Forinstance, the single bearer RAN 106 may transmit the session context tothe second core network, which may transfer the session context to thefirst core network, which may deliver the second context to the dualbearer RAN 102.

In some implementations, the single bearer RAN 106 may also end thesingle 5G bearer 114 used to communicate with the UE 110. For example,the single bearer RAN 106 may sever the single 5G bearer 114 in responseto transmitting the instruction to the UE 110 to transfer the session tothe dual bearer RAN 102.

Although not illustrated in FIG. 1, in some cases, the dual bearer RAN102 and the single bearer RAN 106 may be collocated on the same basestation. Accordingly, in some cases, the single bearer coverage area 108may be substantially contained within the dual bearer coverage area 104.

FIG. 2 illustrates an example environment 200 illustrating interfacesand various elements of a Non-Standalone (NSA) network architecture anda Standalone (SA) network architecture. The example environment 200illustrated in FIG. 2 includes some constituents of the exampleenvironment 100 described above with reference to FIG. 1. For instance,the example environment 200 includes the dual bearer Radio AccessNetwork (RAN) 102, the single bearer RAN 106, the User Equipment (UE)110, the single 5G bearer 114, Position A 116, and Position B 118,described above with reference to FIG. 1.

In the examples illustrated in FIG. 2, the dual bearer RAN 102 mayinclude a master RAN 202 and a secondary RAN 204. As used herein, theterm “master RAN” may refer to a RAN that can communicate wirelesslywith at least one UE and can manages and/or controls wirelesscommunications of at least one secondary RAN with the UE(s). As usedherein, the term “secondary RAN” may refer to a RAN that can communicatewirelessly with one or more UEs according to control plane data receivedfrom a master RAN. For instance, as illustrated in FIG. 2, the masterRAN 202 can control the secondary RAN 204.

A 4G split bearer 206 and a 5G split bearer 208, collectively, may be adual 4G/5G bearer (such as the dual 4G/5G bearer 112 described abovewith reference to FIG. 1). The master RAN 202 may be configured totransmit and/or receive data with the UE 110 over the 4G split bearer206. The 4G split bearer 206 may be a Master Cell Group (MCG) bearer. Asused herein, the term “MCG bearer” can refer to a radio bearer that isserved only by a master RAN. The secondary RAN 204 may be configured totransmit and/or receive data with the UE 110 over the 5G split bearer208. The 5G split bearer 208 may be a Secondary Cell Group (SCG) bearer.As used herein, the term “SCG bearer” can refer to a radio bearer thatis served only by a secondary RAN.

The master RAN 202 and the secondary RAN 204 may be connected to eachother over an X2 interface, which may be a backhaul link between themaster RAN 202 and the secondary RAN 204. In various implementations,the secondary RAN 204 may forward user plane data between the master RAN202 and the UE 110 over the X2 interface. As used herein, the term “userplane data” may refer to data included in user traffic transmittedthroughout one or more networks. For instance, in a voice call in whichvoice services are transmitted between two nodes in a network, userplane data may include data comprising the voice services.

In some cases, the master RAN 202 may control the secondary RAN 204 byexchanging control plane data with the secondary RAN 204 over the X2interface. As used herein, the term “control plane data” may refer todata included in signaling traffic transmitted throughout one or morenetworks. For instance, control plane data may include RRC messages,control messages, or the like, transmitted between two nodes in anetwork.

The master RAN 202 may be connected to a 4G core network 210 via atleast one S1 interface. In some examples, the 4G core network 210 mayinclude an Evolved Packet Core (EPC). In certain instances, variouscomponents of the EPC can include, but are not limited to, a MobilityManagement Entity (MME), a Serving Gateway (SGW), a Packet Data Network(PDN) Gateway (PGW), a Home Subscriber Server (HSS), an Access NetworkDiscovery and Selection Function (ANDSF), and/or an evolved Packet DataGateway (ePDG). An SGW can include a component that handles user-planedata (SGW-U) and a component that handles control-plane data (SGW-C). APDN can include a component that handles user-plane data (PDN-U) and acomponent that handles control-plane data (PDN-C). The EPC may furtherinclude a Policy and Charging Rules Function (PCRF). Each entity,gateway, server, and function in the 4G core network can be implementedby specialized hardware (e.g., one or more devices), general hardwareexecuting specialized software (e.g., at least one virtual machineexecuted on one or more devices), or the like.

The S1 interface(s) may include a first S1 interface interconnecting theMME of the 4G core network 210 and the master RAN 202. In some cases,the S1 interface(s) may include a second S1 interface interconnectingthe SGW of the 4G core network 210 and the master RAN 202.

As illustrated in FIG. 2, the NSA network including the master RAN 202,the secondary RAN 204, and the 4G core network 210 is consistent withOption 3X. However, implementations of the present disclosure can beadopted for other NSA architectures.

The single bearer RAN 106 may be associated with a 5G core network 212.The 5G core network 212 may be, for example, a 5G Core (5GC). In someexamples, various components of the 5GC can include, but are not limitedto, a Network Exposure Function (NEF), a Network Resource Function(NRF), an Authentication Server Function (AUSF), an Access and Mobilitymanagement Function (AMF), a Policy Control Function (PCF), a SessionManagement Function (SMF), a Unified Data Management (UDM) function, aUser Plane Function (UPF), and/or an Application Function (AF). Eachentity, gateway, server, and function in the 5G core network can beimplemented by specialized hardware (e.g., one or more devices), generalhardware executing specialized software (e.g., at least one virtualmachine executed on one or more devices), or the like.

In general, the AMF can be implemented as a network function includingfunctionality to provide UE-based authentication, authorization,mobility management, etc., to various UEs. In some instances, the AMFcan include functionality to terminate a RAN control plane interfacebetween the UE 110 and other functions. In some instances, the AMF caninclude functionality to perform registration management of the UE 110in the single bearer RAN 106 and/or 5G core network 212, connectionmanagement, reachability management, mobility management, accessauthentication, access authorization, security anchor functionality(e.g., receiving and/or transmitting security keys duringregistration/authorization), and the like.

In general, the UPF can be implemented as a network function includingfunctionality to control data transfer between the UE 110 and thevarious other components. In some instances, the UPF can includefunctionality to act as an anchor point for radio access technology(RAT) handover (e.g., inter and intra), external protocol data unit(PDU) session point of interconnect to an external network (e.g., theInternet), packet routing and forwarding, packet inspection and userplane portion of policy rule enforcement, traffic usage reporting,traffic routing, Quality of Service (QoS) handling for user plane (e.g.,packet filtering, gating, uplink/downlink rate enforcement), uplinktraffic verification, transport level packet marking in the uplink anddownlink, downlink packet buffering and downlink data notificationtriggering, and the like. As can be understood in the context of thisdisclosure, there may be one or more UPFs, which are associated with the5G core network 212 and/or with the UE 110.

The single bearer RAN 106 may be connected to the 5G core network 212 byan N2 interface and/or an N3 interface. In various implementations, theN2 interface may interconnect the AMF in the 5G core network 212 and thesingle bearer RAN 106. In some cases, the N3 interface may interconnectthe UPF in the 5G core network 212 and the single bearer RAN 106.

In various implementations, the 4G core network 210 and the 5G corenetwork 212 may communicate over an N26 interface. In variousimplementations, the N26 interface can interconnect the MME in the 4Gcore network 210 and the AMF in the 5G core network 212.

The UE 110 may be configured to communicate with one or more devices inat least one Wide Area Network (WAN) 214. In some cases, the UE 110 maytransmit data to, and receive data from, the device(s) of the WAN(s) 214in one or more communication sessions. In various implementations, theWAN(s) 214 may include one or more Internet Protocol (IP) MultimediaSubsystem (IMS) networks, the Internet, or the like. According tovarious examples, the device(s) exchanging data with the UE 110 may beone or more other UEs, one or more content servers, or the like.

The UE 110 may exchange data with the device(s) of the WAN(s) 214 via aNSA network or a SA network. The NSA network may include the master RAN202 and the secondary RAN 204 of the dual bearer RAN 102, as well as the4G core network 210. The SA network may include the single bearer RAN106 and the 5G core network 212.

In some examples, the master RAN 202 of the dual bearer RAN 102 maycause a session between the UE 110 and the device(s) of the WAN(s) 214to be handed over from the NSA network to the SA network. When thesession is being provided by the NSA network, user plane data in thesession may traverse the 4G core network 210, at least one S1 interfacebetween the master RAN 202 and the 4G core network 210, the master RAN202, the 4G split bearer 206, the X2 interface between the master RAN202 and the secondary RAN 204, the secondary RAN 204, and the 5G splitbearer 208.

In various implementations, the master RAN 202 may transmit, over the 4Gsplit bearer 206, a message indicating a first threshold that can beused to assess a strength and/or quality of a signal received from thesingle bearer RAN 106. In some cases, the message may further indicate asecond threshold that can be used to asses a strength and/or quality ofa signal received from the dual bearer RAN 102. The signal received fromthe dual bearer RAN 102 may be a signal transmitted by the master RAN202 over the 4G split bearer 206 and/or a signal transmitted by thesecondary RAN 204 over the 5G split bearer 208.

If the UE 110 determines that the strength and/or quality of the signalreceived from the single bearer RAN 106 exceeds the first thresholdand/or that the strength and/or quality of the signal received from thedual bearer RAN 102 is lower than the second threshold, the UE 110 maytransmit a report to the master RAN 202. In response to receiving thereport, the master RAN 202 may trigger handover from the NSA network tothe SA network.

In some cases, the master RAN 202 may initiate handover from the 4G corenetwork 210 to the 5G core network 212. For instance, the master RAN 202may transmit, over the S1 interface, a request to hand over the sessionto the 5G core network 212. In response to the request, the 4G corenetwork 210 may transmit, to the 5G core network 212, a session transferrequest over the N26 interface. Upon receiving the session, the 5G corenetwork 212 may confirm that the session has been transferred bytransmitting a message over the N26 interface. The 4G core network 210may transmit a message, to the master RAN 202, confirming that thesession has been handed over to the 5G core network 212.

In various examples, the master RAN 202 may initiate handover of thesession from the dual bearer RAN 102 to the single bearer RAN 106.According to some cases, the master RAN 202 may initiate the handoverbetween the dual bearer RAN 102 and the single bearer RAN 106 inresponse to confirming that the session has been handed over to the 5Gcore network 212. In example implementations, the master RAN 202 maytransmit, to the UE 110 over the 4G split bearer 206, a request toconnect to the single bearer RAN 106. In response, the UE 110 mayestablish a connection with the single bearer RAN 106 and exchange datawith the single bearer RAN 106 over the single 5G bearer 114. The dualbearer RAN 102 may also transmit context data associated with thesession to the single bearer RAN 106 (e.g., via a network path includingthe S1 interface(s), the 4G core network 210, the N26 interface, the 5Gcore network 212, and the N2 and/or N3 interface), which the singlebearer RAN 106 can utilize to continue the session.

In various implementations, because the session has already been handedover to the 5G core network 212, the UE 110 may continue the sessionwith the device(s) of the WAN(s) 214 using the single 5G bearer 114.Accordingly, the session may be supported by the SA network, such thatuser plane data in the session may traverse the 5G core network 212, theN3 interface between the single bearer RAN 106 and the 5G core network212, the single bearer RAN 106, and the single 5G bearer 114.

In some examples, the single bearer RAN 106 may cause a session betweenthe UE 110 and the device(s) of the WAN(s) 214 to be handed over fromthe SA network to the NSA network. When the session is being provided bythe SA network, user plane data may traverse the 5G core network 212,the N3 interface between the single bearer RAN 106 and the 5G corenetwork 212, the single bearer RAN 106, and the single 5G bearer 114.

In various implementations, the single bearer RAN 106 may transmit, overthe single 5G bearer 114, a message indicating a third threshold thatcan be used to assess a strength and/or quality of a signal receivedfrom the dual bearer RAN 102. The signal received from the dual bearerRAN 102 may be a signal transmitted by the master RAN 202 over the 4Gsplit bearer 206 and/or a signal transmitted by the secondary RAN 204over the 5G split bearer 208.

If the UE 110 determines that the strength and/or quality of the signalreceived from the dual bearer RAN 102 exceeds the third threshold, theUE 110 may transmit a report to the single bearer RAN 106. In responseto receiving the report, the single bearer RAN 106 may trigger handoverfrom the SA network to the NSA network.

In some cases, the single bearer RAN 106 may initiate handover from the5G core network 212 to the 4G core network 210. For instance, the singlebearer RAN 106 may transmit, over the N2 interface, a request to acomponent in the 5G core network 212 (e.g., the MME in the 5G corenetwork 212) to hand over the session to the 4G core network 210. Inresponse to the request, the 5G core network 212 (e.g., the MME in the5G core network 212) may transmit, to the 4G core network 210, a sessiontransfer request over the N26 interface. Upon receiving the session, the4G core network 210 may confirm that the session has been transferred bytransmitting a message to the 5G core network 212 over the N26interface. The 5G core network 212 may transmit a message, to the singlebearer RAN 106, confirming that the session has been handed over to the4G core network 210.

In various examples, the single bearer RAN 106 may initiate handover ofthe session from the single bearer RAN 106 to the dual bearer RAN 102.According to some cases, the single bearer RAN 106 may initiate thehandover between the single bearer RAN 106 and the dual bearer RAN 102in response to confirming that the session has been handed over to the4G core network 210. In example implementations, the single bearer RAN106 may transmit, to the UE 110 over the single 5G bearer 114, a requestto connect to the dual bearer RAN 102. In response, the UE 110 mayestablish a connection with the dual bearer RAN 102 and exchange datawith the master RAN 202 over the 4G split bearer 206 and with thesecondary RAN 204 over the 5G split bearer 208. The single bearer RAN106 may also transmit context data associated with the session to thedual bearer RAN 102 (e.g., via a network path including the N2 and/or N3interface, the 5G core network 212, the N26 Interface, the 4G corenetwork 210, and the S1 interface(s)), which the dual bearer 102 canutilize to continue the session.

In various implementations, because the session has already been handedover to the 4G core network 210, the UE 110 may continue the sessionwith the device(s) of the WAN(s) 214 using the 4G split bearer 206 andthe 5G split bearer 208. Accordingly, the session may be supported bythe NSA network, such that user plane data in the session may traversethe 4G core network 210, at least one S1 interface between the masterRAN 202 and the 4G core network 210, the master RAN 202, the 4G splitbearer 206, the X2 interface between the master RAN 202 and thesecondary RAN 204, the secondary RAN 204, and the 5G split bearer 208.

FIG. 3 illustrates example signaling 300 for performing handover of asession between a Non-Standalone (NSA) network and a Standalone (SA)network. The signaling 300 includes data transmitted and/or received bythe User Equipment (UE) described above with reference to FIGS. 1 and 2.In addition, the signaling 300 includes data transmitted and/or receivedby a first Radio Access Network (RAN) 302, a first core network 304, asecond RAN 306, and a second core network 308. In various examples, thefirst RAN 302 may be one of the dual bearer RAN 102 or the single bearerRAN 106 described above with reference to FIGS. 1 and 2, and the secondRAN 306 may be the other one of the dual bearer RAN 102 or the singlebearer RAN 106. Similarly, in various implementations, the first corenetwork 304 may be one of the 4G core network 210 or the 5G core network212 described above with reference to FIG. 2, and the second corenetwork 308 may be the other one of the 4G core network 210 or the 5Gcore network 212. According to example implementations, the first RAN302 and the first core network 304 may be part of one of the NSA networkor the SA network, and the second RAN 306 and the second core network308 may be part of the other one of the NSA network or the SA network.

As illustrated in FIG. 3, first user plane data 310 is exchanged betweenthe UE 110 and the first core network 304 via the first RAN 302. Thefirst user plane data 310 may be part of a communication session betweenthe UE 110 and another device. Services (e.g., data services) can bedelivered to the UE 110 via the first user plane data 310, in variousexamples.

For instance, in scenarios in which the first core network 304 is anEvolved Packet Core (EPC), the first user plane data 310 may betransmitted over a default bearer (e.g., Quality of Service (QoS) ClassIdentifier (QCI) 6, QCI 9, or the like). In some examples in which thefirst core network 304 is a 5GC, the first user plane data 310 may betransmitted over a default 5G QoS Identifier (5QI) (e.g., 5QI6, 5QI9, orthe like).

In some cases in which the first RAN 302 is a dual bearer RAN, the firstuser plane data 310 may be transmitted from an eNodeB to the UE 110 overa Secondary Cell Group (SCG) bearer, to a gNodeB via SCG over an X2interface, and to the UE 110 via a split bearer provided by the gNodeB.

The first RAN 302 may transmit a threshold indicator 312 to the UE 110.In some cases, the threshold indicator 312 may include at least onesignal strength threshold and/or signal quality threshold. Some examplesof a signal strength threshold include a power threshold, such as aReceived Signal Strength Indicator (RSSI), a Reference Signal ReceivedPower (RSRP), or the like. Some examples of a signal quality thresholdmay include a Reference Signal Received Quality (RSRQ), a Signal toInterference plus Noise Ratio (SINR), or the like. The thresholdindicator 312 may further indicate at least one signal to compare to thethreshold(s). For instance, the threshold indicator 312 may indicate aradio signal from the second RAN 306, such as a test signal 314. In somecases, the threshold indicator 312 may further indicate a radio signalfrom the first RAN 302 to compare to the threshold(s). In variousimplementations, the threshold indicator 312 may specify one or morethresholds indicative of a B2 event, an A4 event, or the like.

In various instances, the threshold indicator 312 may comprise a RadioResource Control (RRC) connection reconfiguration message. The RRCmessage may have a measurement control element specifying that awireless band utilized by the second RAN 306 has the highest priority ofany bands utilized by the first RAN 302 or other local RANs. Forinstance, if the second RAN 306 utilizes n71, the RRC connectionreconfiguration may specify that n71 is the highest priority forwireless communication by the UE 110.

The second RAN 306 may transmit the test signal 314 to the UE 110. TheUE 110 may compare the test signal 314 to at least one of thethreshold(s). For example, the UE 110 may determine that the test signal314 has a signal strength that exceeds a signal strength thresholdindicated in the threshold indicator 312. In some cases, the UE 110 maydetermine that the test signal 314 has a signal quality that exceeds asignal quality threshold indicated in the threshold indicator 312.

In some implementations, the UE 110 may further compare a radio signal(not illustrated) received from the first RAN 302 to at least one of thethreshold(s). For instance, the UE 110 may determine that the signalfrom the first RAN 302 has a signal strength that is less than a signalstrength threshold indicated in the threshold indicator 312. In variousexamples, the UE 110 may determine that the signal has a signal qualitythat is less than a signal quality threshold indicated in the thresholdindicator 312.

In response to identifying that the test signal 314 meets a thresholdprovided by the threshold indicator 312 (and, in some cases, that thesignal from the first RAN 302 is below a threshold provided by thethreshold indicator 312), the UE 110 may transmit a measurement report316 to the first RAN 302. The measurement report 316 may indicate thatthe threshold(s) specified by the threshold indicator 312 has beensatisfied.

Upon receiving the measurement report 316, the first RAN 302 mayinitiate handover of the session from the first core network 304 to thesecond core network 308. The first RAN 302 may transmit, to the secondcore network 308, a first handover request 318. The first handoverrequest 318 may be, for instance, a handover preparation message. Thefirst core network 304 may relay the first handover request 318 betweenthe first RAN 302 and the second core network 308. In response toreceiving the first handover request 318, the first core network 304 andthe second core network 308 may cause the session to be handed over fromthe first core network 304 to the second core network 308.

In various implementations, the first handover request 318 may identifythe session. For instance, the first handover request 318 may identifythe UE 110, the first RAN 302, the first core network 304, a type ofservices exchanged in the first user plane data 310, a device exchangingthe first user plane data 310 with the UE 110 via the first RAN 302 andthe first core network 304, or the like. Accordingly, the first corenetwork 304 and/or the second core network 308 may arrange sessionhandover.

In various implementations, the first core network 304 may transmit, tothe second core network 308, a session transfer message. The sessiontransfer message may establish an equivalent bearer or data flow in thesecond core network 308 that was served by the first core network 304 todeliver the first user plane data 310. For instance, if the first corenetwork 304 is an EPC and the second core network 308 is a 5GC, thesecond core network 308 may establish a 5G QoS Indicator (5QI) (e.g.,5QI6) equivalent to the QCI previously used by the first core network304 (e.g., QCI6) to provide the first user plane data 310 to the UE 110.In some examples, if the first core network 304 is a 5GC and the secondcore network 308 is an EPC, the second core network 308 may establish aQCI for the session that is equivalent to a 5QI previously used by thefirst core network 304 to provide the first user plane data 310 to theUE 110.

In response to accepting the session, the second core network 308 maytransmit a handover confirmation 320 to the first RAN 302. The firstcore network 304 may relay the handover confirmation 320 from the secondcore network 308 to the first RAN 302. The handover confirmation 320 mayinform the first RAN 302 that the session has been handed over from thefirst core network 304 to the second core network 308.

In response to receiving the handover confirmation 320, the first RAN302 may initiate handover of the session from the first RAN 302 to thesecond RAN 306. The first RAN 302 may transmit a second handover request322 to the UE 110. In various implementations, the second handoverrequest 322 may identify the second RAN 306. In some cases, the secondhandover request 322 may include an RRC connection request.

According to some implementations, the first RAN 302 may also transmit,to the UE 110, an RRC connection reconfiguration message requesting thatthe existing bearer between the first RAN 302 and the UE 110 (e.g., theSCG bearer) be removed. In some cases, the UE 110 may respond bytransmitting, to the first RAN 302, an RRC connection reconfigurationcomplete message confirming that the existing bearer has been removed.

In accordance with the second handover request 322, the UE 110 maytransmit a connection request 324 to the second RAN 306. In some cases,the UE 110 may attach to, exchange Session Initiation Protocol (SIP)messages, and/or synchronize with the second RAN 306. The connectionrequest 324 may identify the existing session. Accordingly, the secondRAN 306 may accept the session. Upon accepting the session, the secondRAN 306 may transmit a connection confirmation 326 to the UE 110.

Once the session has been handed over to the second core network 308, aswell as to the second RAN 306, the UE 110 and the second core network308 may exchange second user plane data 328. The second user plane data328 may be relayed between the UE 110 and the second core network 308 bythe second RAN 306. The second user plane data 328 may be part of thesame session as the first user plane data 310.

Although not illustrated in FIG. 3, the first RAN 302 may receive thirduser plane data in the session during the signaling 300. The third userplane data may represent context data in the session. For instance, thefirst RAN 302 may receive at least a portion of the third user planedata from the first core network 304 prior to the session being handedover from the first core network 304 to the second core network 308. Insome cases, the first RAN 302 may receive at least a portion of thethird user plane data from the UE 110 prior to the session being handedover from the first RAN 302 to the second RAN 306. In variousimplementations, the first RAN 302 may transmit the third user planedata to the second RAN 306 in response to transmitting the secondhandover request 322 to the UE 110. Accordingly, the third user planedata may be prevented from being lost as the session is handed over fromthe first RAN 302 and the first core network 304 to the second RAN 306and the second core network 308.

Because the first RAN 302 may exchange the first user plane data 310with a first one of a dual bearer and a single bearer, and the secondRAN 306 may exchange the second user plane data 328 with the other oneof the dual bearer and the single bearer, the signaling 300 can be usedto hand over a session from a NSA network to a SA network and/or to handover a session from an SA network to a NSA network. In variousimplementations, resources in the NSA network can be conserved whilealso ensuring that high-throughput and low-latency 5G services can beconsistently delivered to the UE 110.

FIGS. 4 and 5 illustrate example processes in accordance withembodiments of the disclosure. These processes are illustrated aslogical flow graphs, each operation of which represents a sequence ofoperations that can be implemented in hardware, software, or acombination thereof. In the context of software, the operationsrepresent computer-executable instructions stored on one or morecomputer-readable storage media that, when executed by one or moreprocessors, perform the recited operations. Generally,computer-executable instructions include routines, programs, objects,components, data structures, and the like that perform particularfunctions or implement particular abstract data types. The order inwhich the operations are described is not intended to be construed as alimitation, and any number of the described operations can be combinedin any order and/or in parallel to implement the processes.

FIG. 4 illustrates a process 400 for handing over a session between anetwork having a Non-Standalone (NSA) architecture and a network havinga Standalone (SA) architecture. In various implementations, the process400 can be performed by a base station, a Radio Access Network (RAN)(e.g., the dual bearer RAN 102, the single bearer RAN 106, the masterRAN 202, the secondary RAN 204, etc.), an Access Point (AP), or thelike. In various cases, the process 400 can be performed by a componentin a network (e.g., the network having the NSA architecture or thenetwork having the SA architecture) from which the session is beinghanded over.

At 402, a measurement report is received from a User Equipment (UE)associated with a communication session. In various implementations, anindication of one or more thresholds may be transmitted to the UE. Forinstance, a first threshold to compare to a signal transmitted to the UEby a dual bearer RAN and/or a second threshold to compare to a signaltransmitted to the UE by a single bearer RAN may be transmitted to theUE (e.g., by the entity performing the process 400). Each one of thethresholds may be a signal strength threshold, a signal qualitythreshold, or the like. The UE may receive signals from the dual bearerRAN and/or the single bearer RAN and compare the signals to the firstthreshold and/or the second threshold. Based on the comparisons, the UEmay transmit the measurement report.

In some implementations, the UE may be receiving services (e.g., dataservices) in the communication session from a NSA network. The NSAnetwork may transmit a first threshold to compare to a signaltransmitted by the NSA network and a second threshold to compare to asignal transmitted by an SA network. If the signal transmitted by theNSA network is below the first threshold and the signal transmitted bythe SA network is above the second threshold, the UE may generate andtransmit the measurement report to the entity performing the process400.

In example implementations, the UE may be receiving services in thecommunication session from an SA network. The SA network may transmit athird threshold to compare to a signal transmitted by an NSA network. Ifthe signal transmitted by the NSA network is above the third threshold,the UE may generate and transmit the measurement report to the entityperforming the process 400.

At 404, handover of the communication session from a first core networkto a second core network is initiated. In various implementations, 404may include transmitting, to the first core network, a request to handover the communication session to the second core network. The firstcore network may forward the request to the second core network. Thefirst core network and/or the second core network may handover thecommunication session from the first core network to the second corenetwork.

In some implementations, the UE may be receiving services in thecommunication session from the NSA network. The first core network maybe a 4G core network. The second core network may be a 5G core network.

In some cases, the UE may be receiving services in the communicationsession from the SA network. The first core network may be a 5G corenetwork. The second core network may be a 4G core network.

At 406, handover of the communication session between a single radiobearer and a dual radio bearer is initiated. In various examples, ahandover confirmation message may be received from the first corenetwork and/or the second core network. The handover confirmationmessage may indicate that core handover has been performed.

In response to receiving the handover confirmation message, the entityperforming 400 may perform 406. In various examples, a handover requestmay be transmitted to the UE. The UE may be connected to a first RANassociated with the first core network. The handover request may causethe UE to connect to a second RAN associated with the second corenetwork. In various implementations, the first RAN may be one of a dualbearer RAN and a single bearer RAN, and the second RAN may be the otherone of the dual bearer RAN and the single bearer RAN. Accordingly, invarious examples, the process 400 may be utilized to hand over a sessionbetween an NSA network and an SA network.

FIG. 5 illustrates a process 500 for transferring session context duringhandover between a network having a Non-Standalone (NSA) architectureand a network having a Standalone (SA) architecture. In variousimplementations, the process 500 can be performed by a base station, aRadio Access Network (RAN) (e.g., the dual bearer RAN 102, the singlebearer RAN 106, the master RAN 202, the secondary RAN 204, etc.), anAccess Point (AP), or the like. In various cases, the process 400 can beperformed by a component in a network (e.g., the network having the NSAarchitecture or the network having the SA architecture) from which thesession is being handed over.

At 502, handover of a session from a first network to a second networkis initiated. The session may include the exchange of user plane databetween a User Equipment (UE) and another device via the first network.The first network may have a first architecture and the second networkmay have a second architecture. For instance, the first network may havean NSA network architecture and the second network may have an SAnetwork architecture. In some cases, the first network may have an SAnetwork architecture and the second network may have an NSA networkarchitecture.

In various implementations, the first network (e.g., a first RAN in thefirst network) may initiate handover of the session from a first corenetwork in the first network to a second core network in the secondnetwork. In example implementations, the first core network may be a 4Gcore network and the second core network may be a 5G core network, orthe first core network may be a 5G core network and the second corenetwork may be a 4G core network. In some cases, after the session hasbeen handed over from the first core network to the second core network,the first RAN in the first network may initiate handover of the sessionfrom the first RAN to a second RAN in the second network. The handoverfrom the first RAN to the second RAN may be initiated by transmitting ahandover request to the UE. In various examples, the first RAN may be adual bearer RAN and the second RAN may be a single bearer RAN, or thefirst RAN may be a single bearer RAN and the second RAN may be a dualbearer RAN.

At 504, user plane data in the session is received. According to somecases, the user plane data may be received by the first RAN from thefirst network between a first time point at which the handover from thefirst core network to the second core network is initiated and a secondtime point at which the handover from the first core network to thesecond core network is completed. In various examples, the user planedata may be received by the first RAN from the UE between the secondtime point and a third time point at which the handover of the sessionfrom the first RAN to the second RAN has been initiated.

At 506, the handover is determined to be completed. In some cases, thehandover may be determined to be completed in response to the first RANtransmitting the handover request to the UE. In various examples, thehandover may be determined to be completed in response to waiting apredetermined period of time (e.g., 10-30 milliseconds) after thehandover request has been transmitted to the UE. In someimplementations, a confirmation that the handover has been completed maybe received from the second RAN, the UE, or a combination thereof. Uponcompletion of the handover, the session may be handed over to the secondcore network as well as the second RAN.

At 508, the user plane data is transmitted to the second network. Invarious implementations, the user plane data may be transmitted to thesecond RAN in the second network. The second RAN may forward the userplane data to its destination (e.g., to the UE or to the devicecommunicating with the UE). Accordingly, the user plane data that isreceived by the first RAN during handover latency may be retained duringthe handover process.

FIG. 6 illustrates example devices 600 configured to initiate handoverbetween a Non-Standalone (NSA) network and a Standalone (SA) network. Insome embodiments, some or all of the functionality discussed inconnection with FIGS. 1-5 can be implemented in the device(s) 600.Further, the device(s) 600 can be implemented as one or more servercomputers, at least one network element on a dedicated hardware, as atleast one software instance running on a dedicated hardware, or as atleast one virtualized function instantiated on an appropriate platform,such as a cloud infrastructure, and the like. It is to be understood inthe context of this disclosure that the device(s) 600 can be implementedas a single device or as a plurality of devices with components and datadistributed among them.

As illustrated, the device(s) 600 can include one or more radio devices602 and one or more core devices 604. The radio device(s) 602 maycomprise, for instance, an eNodeB, a gNodeB, or any other deviceconfigured to transmit and/or receive data wirelessly from an externaldevice (e.g., a User Equipment (UE)). The radio device(s) 602 cancomprise a memory 606. In various embodiments, the memory 606 isvolatile (including a component such as Random Access Memory (RAM)),non-volatile (including a component such as Read Only Memory (ROM),flash memory, etc.) or some combination of the two.

The memory 606 may include various components, such as a handoverinitiator 608. The handover initiator 608 can comprise methods, threads,processes, applications, or any other sort of executable instructions.The handover initiator 608, and various other elements stored in thememory 606, can also include files and databases.

The memory 606 may include various instructions (e.g., instructions inthe handover initiator 608), which can be executed by at least oneprocessor 610 to perform operations. In some embodiments, theprocessor(s) 610 includes a Central Processing Unit (CPU), a GraphicsProcessing Unit (GPU), or both CPU and GPU, or other processing unit orcomponent known in the art.

The radio device(s) 602 can also include additional data storage devices(removable and/or non-removable) such as, for example, magnetic disks,optical disks, or tape. Such additional storage can include removablestorage 612 and non-removable storage 614. Tangible computer-readablemedia can include volatile and nonvolatile, removable and non-removablemedia implemented in any method or technology for storage ofinformation, such as computer readable instructions, data structures,program modules, or other data. The memory 606, removable storage 612,and non-removable storage 614 are all examples of computer-readablestorage media. Computer-readable storage media include, but are notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, Digital Versatile Discs (DVDs), Content-Addressable Memory(CAM), or other optical storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to store the desired information and which canbe accessed by the radio device(s) 602. Any such tangiblecomputer-readable media can be part of the radio device(s) 602.

The radio device(s) 602 also can include input device(s) 616, such as akeypad, a cursor control, a touch-sensitive display, voice input device,etc., and output device(s) 618 such as a display, speakers, printers,etc. These devices are well known in the art and need not be discussedat length here. In particular implementations, a user can provide inputto the radio device(s) 602 via a user interface associated with theinput device(s) 616 and/or the output device(s) 618.

The radio device(s) 602 can also include one or more wired or wirelesstransceiver(s) 620. For example, the transceiver(s) 620 can include aNetwork Interface Card (NIC), a network adapter, a Local Area Network(LAN) adapter, or a physical, virtual, or logical address to connect tothe various base stations or networks contemplated herein, for example,or the various user devices and servers. To increase throughput whenexchanging wireless data, the transceiver(s) 620 can utilizeMultiple-Input/Multiple-Output (MIMO) technology. The transceiver(s) 620can include any sort of wireless transceivers capable of engaging inwireless, Radio Frequency (RF) communication. The transceiver(s) 620 canalso include other wireless modems, such as a modem for engaging inWi-Fi, WiMAX, Bluetooth, or infrared communication.

In some implementations, the transceiver(s) 620 can be used tocommunicate between various functions, components, modules, or the like,that are comprised in the devices 600. For instance, the transceiver(s)620 can be used to transmit data between the radio device(s) 602 and anexternal User Equipment (UE), between the radio device(s) 602 and thecore device(s) 604, or the like.

In various implementations, the radio device(s) 602 may support dualand/or single connectivity. For instance, the transceiver(s) 620 maysupport communication with the UE via a dual bearer or a single bearer.In some cases, the transceiver(s) 620 are configured to transmit and/orreceive data wirelessly over one or more 5G-specific radio resources,one or more 4G-specific radio resources, or a combination thereof.

In various examples, the core device(s) 604 can include at least one ofa 2G core network, a 3G core network, a 4G core network (e.g., anEvolved Packet Core (EPC)), or a 5G core network. For instance, the coredevice(s) 604 may include an EPC or 5G core network.

The core device(s) 604 can comprise a memory 622. In variousembodiments, the memory 622 is volatile (including a component such asRAM), non-volatile (including a component such as ROM, flash memory,etc.) or some combination of the two.

The memory 622 may include various components, such as coreinstruction(s) 624. The core instruction(s) 624 can comprise methods,threads, processes, applications, or any other sort of executableinstructions. The core instruction(s) 624, and various other elementsstored in the memory 622 can also include files and databases.

The memory 622 may include various instructions (e.g., instructions inthe core instruction(s) 624), which can be executed by at least oneprocessor 626 to perform operations. In some embodiments, theprocessor(s) 626 includes a CPU, a GPU, or both CPU and GPU, or otherprocessing unit or component known in the art.

The core device(s) 604 can also include additional data storage devices(removable and/or non-removable) such as, for example, magnetic disks,optical disks, or tape. Such additional storage can include removablestorage 628 and non-removable storage 630. Tangible computer-readablemedia can include volatile and nonvolatile, removable and non-removablemedia implemented in any method or technology for storage ofinformation, such as computer readable instructions, data structures,program modules, or other data. The memory 622, removable storage 628,and non-removable storage 630 are all examples of computer-readablestorage media. Computer-readable storage media include, but are notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, DVDs, CAM, or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can be accessed by the core device(s) 604. Any such tangiblecomputer-readable media can be part of the core device(s) 604.

The core device(s) 604 also can include input device(s) 632, such as akeypad, a cursor control, a touch-sensitive display, voice input device,etc., and output device(s) 634 such as a display, speakers, printers,etc. These devices are well known in the art and need not be discussedat length here. In particular implementations, a user can provide inputto the core device(s) 604 via a user interface associated with the inputdevice(s) 632 and/or the output device(s) 634.

The core device(s) 604 can also include one or more wired or wirelesstransceiver(s) 636. For example, the transceiver(s) 636 can include aNIC, a network adapter, a LAN adapter, or a physical, virtual, orlogical address to connect to the various base stations or networkscontemplated herein, for example, or the various user devices andservers. To increase throughput when exchanging wireless data, thetransceiver(s) 636 can utilize MIMO technology. The transceiver(s) 636can include one or more wireless transceivers capable of engaging inwireless, RF communication. The transceiver(s) 636 can also includeother wireless modems, such as a modem for engaging in Wi-Fi, WiMAX,Bluetooth, or infrared communication.

In some implementations, the transceiver(s) 636 can be used tocommunicate between various functions, components, modules, or the like,that are comprised in the device(s) 600. For instance, thetransceiver(s) 636 can be used to transmit data between the coredevice(s) 604 and the radio device(s) 602, between the core device(s)604 and another network (e.g., an IP Multimedia Subsystem (IMS) network,data network, the Internet, another core network, etc.), or the like.

Example Clauses

The following clauses provide various implementations of the presentdisclosure:

-   -   A. A method performed by dual-bearer Radio Access Network (RAN),        the method including: receiving, from an Evolved Packet Core        (EPC), user plane data associated with a communication session;        transmitting, to a User Equipment (UE) via a Non-Standalone        (NSA) dual radio bearer, the user plane data; transmitting, to        the UE, first control plane data indicating a first B2 radio        signal threshold and a second B2 radio signal threshold;        receiving, from the UE, second control plane data indicating        that a first radio signal received by the UE over the dual radio        bearer is below the first B2 radio signal threshold and a second        radio signal received by the UE over a single radio bearer is        above the second B2 radio signal threshold; in response to        receiving the second control plane data, transmitting, to the        EPC, third control plane data instructing the EPC to hand over        the communication session to a 5th Generation (5G) Core (5GC);        receiving, from the EPC, fourth control plane data indicating        the communication session has been handed over to the 5GC; and        transmitting, to the UE, a Radio Resource Control (RRC) message        instructing the UE to hand over the communication session to a        single bearer RAN supporting the single radio bearer.    -   B. The method of clause A, wherein the user plane data is first        user plane data, the method further including: receiving, from        the EPC, second user plane data associated with the        communication session; and transmitting, to the single bearer        RAN, the second user plane data.    -   C. The method of clause A or B, wherein the dual radio bearer        includes a 4th Generation (4G) radio bearer and a first 5G radio        bearer, and wherein the single radio bearer includes a second 5G        radio bearer.    -   D. A system including: at least one processor; and memory        storing instructions that, when executed by the at least one        processor, cause the at least one processor to perform        operations including: receiving, from a User Equipment (UE), a        measurement report indicating that a signal threshold has been        satisfied; in response to receiving the measurement report,        initiating handover of a communication session associated with        the UE from a first core network to a second core network;        receiving a message confirming that the communication session        has been handed over from the first core network to the second        core network; and in response to receiving the message,        initiating handover of the communication session between a        single radio bearer associated with a first Radio Access        Technology (RAT) and a dual radio bearer associated with the        first RAT and a second RAT.    -   E. The system of clause D, wherein initiating handover of the        communication session between the single radio bearer and the        dual radio bearer includes initiating handover from the single        radio bearer to the dual radio bearer.    -   F. The system of clause E, wherein the operations further        include: transmitting, to the UE over the single radio bearer, a        message indicating the signal threshold, wherein the measurement        report indicates that a signal strength or signal quality of        radio signal received by the UE over the dual radio bearer is        greater than the signal threshold.    -   G. The system of clause E or F, wherein the first core network        includes a 5th Generation (5G) Core (5GC) and the second core        network includes an Evolved Packet Core (EPC).    -   H. The system of any one of clauses E to G, wherein initiating        handover of the communication session between the single radio        bearer and the dual radio bearer includes initiating handover        from the dual radio bearer to the single radio bearer.    -   I. The system of clause H, wherein the signal threshold is a        first signal threshold, and the operations further include:        transmitting, to the UE over the dual radio bearer, a message        indicating the first signal threshold and a second signal        threshold, wherein the measurement report indicates that a first        signal strength or first signal quality of a first radio signal        received by the UE over the single radio bearer exceeds the        first signal threshold and that a second signal strength or        second signal quality of second radio signal received by the UE        over the dual radio bearer is less than the second signal        threshold.    -   J. The system of clause H, wherein the first core network        includes an Evolved Packet Core (EPC) and the second core        network includes a 5th Generation (5G) Core (5GC).    -   K. The system of any one of clauses D to J, wherein the first        RAT includes a 5th Generation (5G) RAT and the second RAT        includes a 4th Generation (4G) RAT.    -   L. The system of any one of clauses D to K, wherein the        operations further include: in response to initiating handover        of the communication session from the first core network to the        second core network, receiving user plane data associated with        the communication session from the first core network;        determining that the handover of the communication session        between the single radio bearer the dual radio bearer is        completed; and in response to determining that the handover of        the communication session between the single radio bearer and        the dual radio bearer is completed, transmitting the user plane        data to a Radio Access Network (RAN) associated with the second        core network.    -   M. A method including: receiving, from a User Equipment (UE), a        measurement report indicating that a signal threshold has been        satisfied; in response to receiving the measurement report,        initiating handover of a communication session associated with        the UE from a first core network to a second core network;        receiving a message confirming that the communication session        has been handed over from the first core network to the second        core network; and in response to receiving the message,        initiating handover of the communication session between a        single radio bearer associated with a first Radio Access        Technology (RAT) and a dual radio bearer associated with the        first RAT and a second RAT.    -   N. The method of clause M, wherein initiating handover of the        communication session between the single radio bearer and the        dual radio bearer includes initiating handover from the single        radio bearer to the dual radio bearer.    -   O. The method of clause N, further including: transmitting, to        the UE over the single radio bearer, a message indicating the        signal threshold, wherein the measurement report indicates that        a signal strength or signal quality of radio signal received by        the UE over the dual radio bearer is greater than the signal        threshold.    -   P. The method of clause N or O, wherein the first core network        includes a 5th Generation (5G) Core (5GC) and the second core        network includes an Evolved Packet Core (EPC).    -   Q. The method of any one of clauses M to P, wherein initiating        handover of the communication session between the single radio        bearer and the dual radio bearer includes initiating handover        from the dual radio bearer to the single radio bearer.    -   R. The method of clause Q, wherein the signal threshold is a        first signal threshold, and the method further includes:        transmitting, to the UE over the dual radio bearer, a message        indicating the first signal threshold and a second signal        threshold, wherein the measurement report indicates that a first        signal strength or first signal quality of a first radio signal        received by the UE over the single radio bearer exceeds the        first signal threshold and that a second signal strength or        second signal quality of second radio signal received by the UE        over the dual radio bearer is less than the second signal        threshold.    -   S. The method of clause R, wherein the first core network        includes an Evolved Packet Core (EPC) and the second core        network includes a 5th Generation (5G) Core (5GC).    -   T. The method of any one of clauses M to S, further includes: in        response to initiating handover of the communication session        from the first core network to the second core network,        receiving user plane data in the communication session from the        first core network; determining that the handover of the        communication session between the single radio bearer the dual        radio bearer is completed; and in response to determining that        the handover of the communication session between the single        radio bearer and the dual radio bearer is completed,        transmitting the user plane data to a Radio Access Network (RAN)        associated with the second core network.

CONCLUSION

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described. Rather,the specific features and acts are disclosed as exemplary forms ofimplementing the claims.

What is claimed is:
 1. A method performed by dual-bearer Radio AccessNetwork (RAN), the method comprising: receiving, from an Evolved PacketCore (EPC), first user plane data associated with a communicationsession; transmitting, to a User Equipment (UE) via a Non-Standalone(NSA) dual radio bearer, the first user plane data; transmitting, to theUE, first control plane data indicating a first B2 radio signalthreshold and a second B2 radio signal threshold; receiving, from theUE, second control plane data indicating that a first radio signalreceived by the UE over the dual radio bearer is below the first B2radio signal threshold and a second radio signal received by the UE overa single radio bearer is above the second B2 radio signal threshold; inresponse to receiving the second control plane data, transmitting, tothe EPC, third control plane data instructing the EPC to hand over thecommunication session to a 5th Generation (5G) Core (5GC); in responseto transmitting the third control plane data, receiving, from the EPC,second user plane data associated with the communication session;receiving, from the EPC, fourth control plane data indicating thecommunication session has been handed over to the 5GC; transmitting, tothe UE, a Radio Resource Control (RRC) message instructing the UE tohand over the communication session to a single bearer RAN supportingthe single radio bearer; and in response to transmitting the RRCmessage, transmitting, to the 5GC, the second user plane data.
 2. Themethod of claim 1, wherein the dual radio bearer comprises a 4thGeneration (4G) radio bearer and a first 5G radio bearer, and whereinthe single radio bearer comprises a second 5G radio bearer.
 3. A systemcomprising: at least one processor; and memory storing instructionsthat, when executed by the at least one processor, cause the at leastone processor to perform operations comprising: receiving, from a UserEquipment (UE), a measurement report indicating that a signal thresholdhas been satisfied; in response to receiving the measurement report,initiating handover of a communication session associated with the UEfrom a first core network to a second core network; in response toinitiating handover of the communication session from the first corenetwork to the second core network, receiving user plane data associatedwith the communication session from the first core network; receiving amessage confirming that the communication session has been handed overfrom the first core network to the second core network; in response toreceiving the message, initiating handover of the communication sessionbetween a single radio bearer associated with a first Radio AccessTechnology (RAT) and a dual radio bearer associated with the first RATand a second RAT; determining that the handover of the communicationsession between the single radio bearer and the dual radio bearer iscompleted; and in response to determining that the handover of thecommunication session between the single radio bearer and the dual radiobearer is completed, transmitting the user plane data to the second corenetwork.
 4. The system of claim 3, wherein initiating handover of thecommunication session between the single radio bearer and the dual radiobearer comprises initiating handover from the single radio bearer to thedual radio bearer.
 5. The system of claim 4, wherein the operationsfurther comprise: transmitting, to the UE over the single radio bearer,a message indicating the signal threshold, wherein the measurementreport indicates that a signal strength or signal quality of radiosignal received by the UE over the dual radio bearer is greater than thesignal threshold.
 6. The system of claim 4, wherein the first corenetwork comprises a 5th Generation (5G) Core (5GC) and the second corenetwork comprises an Evolved Packet Core (EPC).
 7. The system of claim3, wherein initiating handover of the communication session between thesingle radio bearer and the dual radio bearer comprises initiatinghandover from the dual radio bearer to the single radio bearer.
 8. Thesystem of claim 7, wherein the signal threshold is a first signalthreshold, and the operations further comprise: transmitting, to the UEover the dual radio bearer, a message indicating the first signalthreshold and a second signal threshold, wherein the measurement reportindicates that a first signal strength or first signal quality of afirst radio signal received by the UE over the single radio bearerexceeds the first signal threshold and that a second signal strength orsecond signal quality of second radio signal received by the UE over thedual radio bearer is less than the second signal threshold.
 9. Thesystem of claim 7, wherein the first core network comprises an EvolvedPacket Core (EPC) and the second core network comprises a 5th Generation(5G) Core (5GC).
 10. The system of claim 3, wherein the first RATcomprises a 5th Generation (5G) RAT and the second RAT comprises a 4thGeneration (4G) RAT.
 11. The system of claim 3, wherein receiving theuser plane data associated with the communication session from the firstcore network comprises receiving the user plane data over an S1interface.
 12. The system of claim 11, wherein transmitting the userplane data to the second core network comprises transmitting the userplane data to the second core network via the S1 interface and an N26interface connecting the first core network to the second core network.13. A method comprising: receiving, from a User Equipment (UE), ameasurement report indicating that a signal threshold has beensatisfied; in response to receiving the measurement report, initiatinghandover of a communication session associated with the UE from a firstcore network to a second core network; in response to initiatinghandover of the communication session from the first core network to thesecond core network, receiving user plane data in the communicationsession from the first core network; receiving a message confirming thatthe communication session has been handed over from the first corenetwork to the second core network; in response to receiving themessage, initiating handover of the communication session between asingle radio bearer associated with a first Radio Access Technology(RAT) and a dual radio bearer associated with the first RAT and a secondRAT; determining that the handover of the communication session betweenthe single radio bearer and the dual radio bearer is completed; and inresponse to determining that the handover of the communication sessionbetween the single radio bearer and the dual radio bearer is completed,transmitting the user plane data to the second core network.
 14. Themethod of claim 13, wherein initiating handover of the communicationsession between the single radio bearer and the dual radio bearercomprises initiating handover from the single radio bearer to the dualradio bearer.
 15. The method of claim 14, further comprising:transmitting, to the UE over the single radio bearer, a messageindicating the signal threshold, wherein the measurement reportindicates that a signal strength or signal quality of radio signalreceived by the UE over the dual radio bearer is greater than the signalthreshold.
 16. The method of claim 14, wherein the first core networkcomprises a 5th Generation (5G) Core (5GC) and the second core networkcomprises an Evolved Packet Core (EPC).
 17. The method of claim 13,wherein initiating handover of the communication session between thesingle radio bearer and the dual radio bearer comprises initiatinghandover from the dual radio bearer to the single radio bearer.
 18. Themethod of claim 17, wherein the signal threshold is a first signalthreshold, and the method further comprises: transmitting, to the UEover the dual radio bearer, a message indicating the first signalthreshold and a second signal threshold, wherein the measurement reportindicates that a first signal strength or first signal quality of afirst radio signal received by the UE over the single radio bearerexceeds the first signal threshold and that a second signal strength orsecond signal quality of second radio signal received by the UE over thedual radio bearer is less than the second signal threshold.
 19. Themethod of claim 18, wherein the first core network comprises an EvolvedPacket Core (EPC) and the second core network comprises a 5th Generation(5G) Core (5GC).
 20. The method of claim 13, wherein receiving the userplane data associated with the communication session from the first corenetwork comprises receiving the user plane data over an S1 interface.